1. Technical Field
The present invention relates to the use of esters of long chain alcohols and long chain fatty acids as a floatation aid in conjunction with fatty acids in the froth floatation process for the benefaction of ores. This invention also relates to the process for ore beneficiation by floatation. More specifically, this invention relates to the replacement of petroleum hydrocarbons, used in the froth floatation step, with esters that are readily or inherently biodegradable.
2. Prior Art
Froth floatation has been widely used over several decades to remove clays and sand from calcium phosphate ores. This process is capable of treating relatively low grades of ore into concentrated fractions suitable for further processing. Typically, the ore is slurried to make an aqueous dispersion. The aqueous slurry is then conditioned by agitating the slurry in the presence of various chemicals. The treated slurry is pumped into a floatation cell which introduces dispersed air in the form of fine bubbles. The chemicals enhance the selectivity of the fine air bubbles to adhere to the ore's surface to form a froth highly concentrated with the desired ore and is removed by mechanical means. The most common process employed by the phosphate industry is the Crago process invented in the 1940's. It utilizes three steps to enrich the ore: anionic floatation, scrubbing, and cationic floatation.
There are a tremendous number of articles and patents which address the anionic floatation reagents. The following is a sample of some of those inventions.
U.S. Pat. No. 6,994,786 B2 discloses a method of phosphate beneficiation which employs methyl and ethyl fatty acid esters that are biodegradable. Although the data presented appears to indicate that the methyl and ethyl esters can replace fuel oil, it appears that the alcohol chain length is too small for efficient adhesion.
U.S. Pat. No. 6,871,743 B2 discloses a method of phosphate beneficiation with increased floatation rate by enhancing the hydrophobicity of the particles so they can be more readily collected by the air bubbles. This patent reinforces the notion that the methyl and ethyl esters are not hydrophobic enough for a desired level of floatation.
Accordingly, there is always a need for improved froth floatation processes for the benefaction of ores. It is to these needs, among others, that this invention is directed.